Ultrasonic welding has been used for bonding in a number of materials. Most commonly, ultrasonic bonding is utilized in theremoplastic materials. Recently, it has been discovered that ultrasonic spot welding could be accomplished. See, for example, the November-December 1980 issue of Plastics Design Forum, page 86. This publication recognizes the existence of ultrasonic spot welding as well as its advantage in producing a clean appearance on the surface opposite the weld. This article recognizes that the standard tip is inserted one and one-half times the thickness of a sheet of material. The article further recognizes the possibility of inverse spot welding, that is fitting the tip to the mounting fixture or anvil and utilizing a flat faced horn to provide ultrasonic energy.
The use of ultrasonic spot welding is further recognized by an article entitled "Ultrasonic Assembly", by R. A. Clarke published in the 1980-81 Modern Plastics Encyclopedia, page 447-450. In this article, Clarke recognizes the general incorporation of the annular ring design in the horn or tip for ultrasonic spot welding.
It is an object of the present invention to produce improved spot welds.
It is another object of the present invention to produce improved spot welds in sheet thermoplastic material.
It is a further object of the present invention to provide these welds along a relatively lengthy weld line and to produce these welds with a tip design which is self-releasing from the sheet material upon completion of the weld.
It is a still further object of the present invention to provide a welding tip which may be used for inverse spot welding in thermoplastic material and which may be removed from contact with the sheet material by displacement only in a direction parallel to the line along which the spot welds are produced.
These and other objects of the present invention will become more fully apparent with reference to the following specification, drawings and claims which relate to the preferred embodiments of the present invention.